Offshore platforms of the so called semi-submersible type comprise an operating deck carried by columns supported by submersible pontoons. In certain embodiments the operating deck has formed part of a strong box structure enclosing a number of tween decks and integrated with the upper ends of the columns. In this manner a very strong and rigid base structure is obtained, where the need for bracings between the columns is reduced. The braces will offer a certain resistance when the platform is being moved. When the platform is held stationary at the operating field the braces will mean extra surfaces, where waves and currents will impose forces. The points of attachment between the braces and the columns have further shown risks for cracking and fracture.
Semi-submersible platforms used for production, i.e. reception of oil from a previously drilled well, has hitherto lacked storing capacity, so the oil obtained had to be transferred directly to a tanker or to a separate storing facility.
The aim of the present invention is to propose an off-shore platform having an operating deck of sufficient capacity to carry drilling as well as oil recovery equipment, and which is especially strengthened for operation in fields where high service stresses may be encountered The platform furthermore has a significant storing capacity for the oil produced.